Does a musical score hold the secret of hidden Nazi gold? In scenes reminiscent of an Indiana Jones movie, a Dutch film-maker has started digging in a Bavarian town, believing annotations made by Hitler's aide Martin Bormann on a piece of sheet music will guide him to the gold.

The theory was first developed by the Dutch writer Karl Hammer Kaatee last year, when he published scans of decades-old sheet music that was allegedly marked-up by Bormann. There's nothing exceptional about the music – Gottfried Federlein's Marsch-Impromptu – but Kaatee was drawn to the pages' hand-drawn scribbles and mysterious annotations. In the waning days of the second world war, he argued, Bormann used Marsch-Impromptu to secretly convey the location of a buried fortune: at least 100 gold bars, plus Hitler's personal collection of diamonds, known as the "tears of the wolf". The Führer supposedly intended for the document to reach Nazi party accountant Franz Xaver Schwarz in Munich; instead, Schwarz was arrested.

Now, 51-year-old film-maker Leon Giesen believes he has cracked the code and has already staged three excavations in the town of Mittenwald, in Bavaria, guided by Bormann's markings. According to Spiegel Online, Giesen's theory is centred on the hand-written phrase, "Wo Matthias die Saiten Streichelt" ("where Matthew plucks strings"). This, he claims, is a reference to Mittenwald luthier Matthias Klotz, one of the town's most famous residents. Another phrase, "Enden der Tanz" ("end the dance") is purportedly an allusion to one of the local railway's buffer stops. The sheet music may even contain a concealed diagram of the city's train tracks.

Working separately from Kaatee, Giesen is using crowdfunding to finance further Mittenwald digs. The initial drillings were reportedly fruitful: diggers found "anomalous" metals, Giesen told Der Spiegel. "[It] cold be a treasure chest," admitted Jürgen Proske, a local historian and amateur archaeologist, "but it could just be a manhole cover."

It is possible sceptics might look at Karl Hammer Kaatee's other work and doubt the likelihood of the music containing a code. For example, his 2006 book Satan's Song purported to be a fictionalised version of the true story of the CIA's hunt for Jesus.